The invention relates to a system and a tool for joining a coupling element, for example, a joining flange means, to a pipe, said coupling element surrounding the pipe and having grooves facing the pipe and intended to receive a corresponding plurality of beads provided on the pipe and a coupling element connectable to a pipe, said coupling element configured to surround the pipe and having grooves to face the pipe and to receive a corresponding plurality of beads provided on the pipe.
1. Field of the Invention
Flanges of many types and varieties are used extensively in industry when pipe-to-pipe or pipe-to-other component connections are to be provided. The welding of flanges to pipes is the most common method in the case of steel pipes and standard weldable metals, whilst, for example, screw flanges are used in connection with, for instance, galvanised pipes.
2. Description of Related Art
In recent years a number of methods have been developed for the fastening of coupling elements and the joining of pipes by deforming the pipe inside the coupling so as to secure it. Other methods and equipment which clamp the coupling to the outside of the pipe without any or with little deformation of the pipe have also been developed. Examples of such methods are taught in U.S. Pat. No. 4,593,448 and U.S. Pat. No. 4,147,385. DE 27 24 257 and U.S. Pat. No. 2,252,274 teach tools with rollers which by means of a rotating cone in the centre with rollers therearound will deform the pipe so that it fits into grooves in the coupling elements. DE 3144385 teaches a joining system for pipes where radially movable ridges, with the aid of hydraulic pressure against underlying pistons, press in beads. However, as discussed further below, the pipe wall on the side of the beads will buckle inwards, and when the ridges of the tool are retracted, the actual bead in the pipe will also retract somewhat, which makes the connection weak. In addition, there will be a metal-to-metal seal between pipe and coupling element, and therefore the system taught in the said document will require sealing material in the grooves of the coupling element. It has been found that with radial pistons as taught in DE 3144385 it is not possible to obtain an especially large radial force, and this principle could perhaps be used with particularly thin-walled pipes.
To deform a pipe wall into grooves in a surrounding coupling element requires very large forces if the pipe wall is to be pressed radially outwards. The use of rollers as described in DE 27 24 257 and U.S. Pat. No. 2,252,274 means that less radial force is required, but on the other hand the tool must be secured to the pipe and therefore becomes large so and heavy. Rolling subjects the material to harsher treatment and also takes longer than radial pressing.